Bug in iteration over a FPGroup?

[MFrankenbach]

I noticed that when iterating over a finite group, not all elements are visited, and group elements can be visited twice.
Strangely, it looks fine when I only iterate and print:

using Groups
Z3 = FPGroup(FreeGroup(1), [only(gens(F))^3 => one(F)])
for g in Z3
  println(g)
end

gives

(id)
f1
F1

But: As soon as I 'do' something with the gs, elements repeat:

julia> for g in Z3
           push!(v, g)
       end

julia> v
3-element Vector{FPGroupElement}:
 (id)
 f1
 f1

The inverse of f1 is not present in v.

Similar problems occur when creating a dictionary:

julia> d = Dict()
Dict{Any, Any}()

julia> ig = 0
0

julia> for g in Z3
           ig += 1
           d[g]=ig
       end

julia> display(d)
Dict{Any, Any} with 3 entries:
  f1   => 2
  (id) => 1
  f1   => 3

Am I doing something wrong? I'm also wondering why the dictionary can have two keys f1.

[kalmarek]

the issue is that the returned elements actually alias with the internal state of the iterator.

What happens if you replace elt with deepcopy(elt) in this line?

Groups.jl/src/iteration.jl

Line 54 in 1fbd7b8

return elt, state